Supercritical Of Co <sub> 2 </ Sub> Modified And Membrane Preparation Of Biological Materials

Supercritical carbon dioxide (SCCO2) has low viscosity, high diffusivity, and near zero surface tension. Its solvent strength could be continuously tunable from gas-like to liquid-like by changing pressure and/or temperature. In addition, CO2 is nonflammable, nontoxic and has mild critical conditions. Recently, many works had taken advantage of these unique properties of SCCO2 to physical or chemical modification of the polymers. While in most of the grafting modification, the matrices were always the synthetic polymer, such as polypropylene or poly (4-methyl-1-pentene). To the best of our knowledge, there is no study about the modification of natural silk with supercritical fluid technology. Silk is one of the typical natural protein polymers. Grafting has been regarded as a powerful method for improving silk fibers properties. In this work, graft co-polymerizations of MMA and AA onto Antheraea pernyi silk fibers, initiated by BPO and AIBN using SCCO2 as solvent and swelling agent were investigated. Antheraea pernyi silk, a wild type silk, has been used as textile materials as a variation to domestic silk (Bombyx mori). The grafting degree was determined as a function of impregnating pressure, impregnating time, monomer concentration, initiator concentration and reaction time. The structure was determined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetry (TG). The products were also further investigated of their water-retention capacity and mechanical properties.CO2 is miscible with many solvents, but is an antisolvent (nonsolvent) for most polymers. The application of SCCO2 has been finding increasing interests in the preparation of polymer membranes. Membrane formation with SCCO2 as nonsolvent is analogous to the conventional immersion precipitation process using organic nonsolvent. In this paper, polylactide (PLA) membranes were prepared with SCCO2 as nonsolvent at different experimental conditions including solvent, polymer concentration, CO2 pressure, preconditioning, depressurization rate and composition of nonsolvent. The effects of different experimental conditions on the cross-sectionstructure of PLA membranes were investigated through scanning electron microscope (SEM). And polarizing microscope, wide-angle X-ray diffraction (WAXD) and differential scanning calorimeter (DSC) were used to study the crystalline of PLA membranes prepared at different conditions.